Not only can human embryonic stem cells restore damaged hearts, they can also improve heart function and significantly hold back the progression of heart failure, say scientists from the Center for Cardiovascular Biology and Regenerative Medicine at the University of Washington, in Seattle, who carried out experiments on rats.

You can read about this in the journal Nature Biotechnology.

This experiment is seen by numerous scientists as a possible major breakthrough in the repair of damaged heart muscles. Previous attempts with stem cells had been disappointing and several of the cells rapidly died after being transplanted into the heart. The scientists say they have found a way of boost the survival of these cells by creating a survival cocktail. The cells which had received this cocktail were placed into the damaged hearts of mice.

They found that virtually 100% of the rats had human heart muscle grafts in them after receiving the treated stem cells. They had divided the rats into four groups: 1. Rats receiving the treated (with cocktail) cells. 2. Rats receiving cocktail but no cells. 3. Rats receiving non-cardiac cells. 4. Rats receiving solely water injections.

All the rats that were not given heart cells eventually had heart failure. Those that did receive the human heart muscle grafts implanted in them had a complete reversal of the progression of heart failure, according to lead researcher, Dr. Charles Murry.

"In patients who had suffered a heart attack, if we were able to re-muscularize their heart with stem cell-derived heart muscle cells, this should prevent them from developing heart failure. The rub is that the rat is not a person," Murry said.

The team said that a larger study is needed using animals with a slower heartbeat. As a rat's heart beats at 350 times a minute it is possible that a human may experience problems with this procedure which are not present when carried out on rats.